March. 1922] NEWCOMBE BEHAVIOR OF SENSITIVE STIGMAS 
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ception of Tecoma radicans, none of the species reported in this paper keep 
their stigmas closed as long with any other substance tried as with living 
pollen. The behavior of the stigmas of the various species tested in the 
present study indicates the possibility of an enzyme, or other chemical, 
in the pollen and Taka-diastase as the agent in maintaining closure. Starch 
alone is certainl}^ effective in prolonging the closure; so that an enzyme, or 
similar chemical, need not be credited alone with influence on maintaining 
closure. It is difficult to conceive of the pollen maintaining closure or 
causing closure for days merely through the abstraction of water. Is there 
any reason why the stigmatic cells should not replenish their lost water by 
calling on the water supply in the style and parts below? Although the 
stigmas of Catalpa usually close at the beginning of wilting of the flower, 
the stigmas of other species do not close on wilting of the flower, and the 
stigmas remain open even when withering. A loss of water by the cells of 
the stigma, therefore, does not necessarily require the lobes to close. It is 
true that if pollen, flour, and starch take water from the stigma, they take 
it probably from one side; but we do not know that these objects certainly 
take more water from the cells than the cells can recover. It does not seem 
likely either that the absorbing objects continue their water abstraction for 
hours. It would seem probable that the presence of absorbing material 
on the stigmatic surface reduces the resistance of the protoplasm to filtra- 
tion, and that this loss of resistance is gradually recovered except in the 
case of germinating pollen. Such an increase and maintenance of perme- 
abiHty, even though the effect comes slowly, may be a sensitive reaction 
instead of what is usually called a purely physical reaction, as has been 
suggested. 
List of Plants Reported as Having Sensitive Stigmas, with the Authors' Names 
Several authors have reported plants, giving the genus only; such are 
not listed here except in two cases in which no species of the genus has been 
published. Several of the plants listed are horticultural varieties; but I 
have given the names as published by the authors of the papers. 
SCROPHULARIACEAE 
Mimulus guttatus , Kabsch 
M, moschatus Henderson 
M. liiteus Henderson 
M. roseus Henderson 
M. cardinalis Henderson 
M. tillingii Burck 
M, hybridus Burck 
M. liiteus L. var. punctatus Newcombe 
M. glahratus KBK. var, Jamesii T. & G Newcombe 
Torenia Fournieri Burck 
Rehmanma sp Kerner 
Digitalis purpurea L. . . Newcombe 
